Ariel Máximo Cantero, better known as “Guille,” is one of the central figures in the history of Los Monos, a criminal organization that emerged in Rosario, Santa Fe, and became closely associated with drug trafficking, extortion and violent disputes in the region.
Cantero is the son of Ariel Cantero, known as “El Viejo,” who is widely identified as one of the founders of the group. After the death of his brother Claudio Ariel Cantero, known as “El Pájaro,” in 2013, Guille became one of the organization’s principal leaders alongside Ramón Machuca, known as “Monchi.”
His criminal record expanded through a series of judicial proceedings in both provincial and federal courts. In 2018, Cantero received a 22-year sentence for ordering attacks against homes belonging to judicial officials and other targets. Earlier proceedings had also resulted in convictions connected to drug trafficking and other offenses.
One of the most significant cases concerned his alleged ability to continue directing criminal activities while imprisoned. In 2019, a federal court in Rosario sentenced Cantero to ten years for organizing an extortionate kidnapping from prison. According to prosecutors, he coordinated the operation from his cell while being held at Coronda prison. The conviction established his responsibility for the offense.
In 2021, another federal proceeding resulted in a twelve-year sentence for Cantero for organizing drug-trafficking activities and participating in the sale of narcotics. His previous convictions were combined with the new sentence, producing a unified sentence of eighteen years at that stage.
His legal situation changed again in November 2024. The Federal Oral Court No. 3 of Rosario sentenced him to nineteen additional years for organizing aggravated drug trafficking. The court simultaneously unified his existing sentences into a single 48-year prison term. The federal prosecutors' office described him as the maximum reference of Los Monos.
Media reports have calculated the total of Cantero’s individual sentences at more than one hundred years. LA NACION reported in November 2024 that the accumulated sentences reached 132 years, while emphasizing that Argentine law limits the effective maximum period of imprisonment to fifty years.
The distinction between accumulated sentences and actual time of imprisonment is important. The figure of more than one hundred years represents the sum of different judicial sentences rather than a literal requirement to remain incarcerated for that entire period.
Cantero has also been described by organized-crime researchers as continuing to exercise influence over Los Monos while incarcerated. A 2025 report produced under the European Union-supported EL PACCTO program stated that Cantero continued to head the organization from prison and noted that additional judicial rulings had increased the total of sentences attributed to him.
His case has therefore become closely associated with Rosario’s broader struggle against organized crime. Prosecutors have repeatedly investigated structures allegedly operating under the influence of leaders who were themselves already imprisoned. In Cantero’s case, several of the convictions concern conduct that prosecutors said was coordinated from behind bars.
As of 2026, Ariel Máximo “Guille” Cantero remains imprisoned in Argentina. His name continues to appear in judicial and investigative records concerning Los Monos and organized crime in Rosario, while the legal record distinguishes his final convictions from allegations contained in investigations that did not result in convictions.
SOURCES
Argentina’s Public Prosecutor’s Office — Ministerio Público Fiscal
2024: Cantero sentenced to 19 years and unified sentence of 48 years
Argentina’s Public Prosecutor’s Office — Ministerio Público Fiscal
2019: Cantero convicted for organizing an extortionate kidnapping from prison
Argentina’s Public Prosecutor’s Office — Ministerio Público Fiscal
2021: Cantero convicted in a drug-trafficking case
LA NACION
Guille Cantero’s accumulated sentences
InSight Crime
Ariel Máximo Cantero, alias “Guille”
